Multi-Step Rollbacks - kenpachi

When a model calls several tools in one turn — reserve a seat, then charge a card — a failure on step two can leave step one’s side effects in place. kenpachi implements saga-style rollback: register an undo in each tool, and if a later tool in the same batch fails, undos run in reverse order.

Think of registerCompensation as “if anything after me fails, run this cleanup.”

Example

import { z } from "zod";
import { Agent, defineTool } from "kenpachi";

const reserveSeat = defineTool({
  name: "reserve_seat",
  description: "Reserves a seat for a user",
  schema: z.object({ seatId: z.string() }),
  async execute({ seatId }, ctx) {
    console.log(`Reserved seat ${seatId}`);

    // Register compensating action
    ctx.registerCompensation(async () => {
      console.log(`Rollback: Released seat ${seatId}`);
    });

    return { status: "held", seatId };
  },
});

const processPayment = defineTool({
  name: "process_payment",
  description: "Charges user payment card",
  schema: z.object({ amount: z.number() }),
  async execute({ amount }) {
    // Payment fails
    throw new Error("Card declined: Insufficient funds");
  },
});

// If the model calls reserveSeat and processPayment together,
// the reserveSeat hold is automatically released when processPayment throws.

⌘I